Solid state constant current regulator



June 3, 1969 a. R. BOYMEL SOLID STATE CONSTANT CURRENT REGULATOR Filed Aug. 31, 1966 mujmii Swab 121 mu T m M w mam D A 1. R E B ATTORNEY United States Patent SOLID STATE CONSTANT CURRENT REGULATOR Bernard R. Boymel, Washington, D.C., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed Aug. 31, 1966, Ser. No. 576,788

Int. Cl. Gf 1/44 U.S. Cl. 323-4 4 Claims ABSTRACT OF THE DISCLOSURE A constant current regulator which is particularly useful in controlling the load current supplied to an airfield lighting system. The improved regulator utilizes a Hall Effect multiplier that provides an output potential propor tional to the square of the output load current of the lighting system. The Hall Effect multiplier output potential controls energization of a saturable reactor and the phase of a pulse that gates a silicon control rectifier in series with the energizing source for the lighting system. Protective circuitry is provided to prevent damage to the Hall Effect multiplier from overloading.

Various types of constant current regulators have been designed and used in the past to control the energization of airfield lighting systems. Such systems, however, have been found to be too 'bulky and inefiicient for use in mobile tactical military situations where the airfield facility often must be installed or disassembled and removed quickly and easily. Moreover, presently known and used constant current regulators generally employ tuned circuits and movable mechanical parts to achieve the desired control and regulation. These movable and tunable components require constant care and maintenance which are often unavailable in various military situations.

It is therefore a principal object of the present invention to provide a novel and improved constant current regulator which is small, light in weight, and easily transportable.

It is a further object of the present invention to provide a novel and improved constant current regulator wherein the constant current characteristic is obtained without the use of tuned circuits or moving parts which require constant care and maintenance.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing wherein:

The single figure of the drawing is a diagrammatic view of a preferredembodiment of the present invention.

Referring now to the drawing, it will be noted that the input power conductors 3 and 5 are connected to the pri mary winding of the power transformer 7 through control switches 9 and 11 and through the parallel circuit of the inversely connected anode-cathode circuits of silicon control rectifiers 13 and 15. The secondary winding of power transformer 7 is connected to the output circuit of load 17 through the loadammeter 19 and the primary winding of current transformer 21. The parallel connected inductance coils 23 and 25, which provide the magnetic field for the Hall Effect multipliers 27 are connected in series with the major axis of the rectangular Hall semiconductor element 29 across the secondary winding of current transformer 21. The parallel arrangement of the inversely connected silicon control rectifiers 31 and 33 is connected in series with the primary winding of transformer 35 across the Hall semiconductor element 29. Opposite ends of the secondary winding of transformer 35 are coupled to ground through diodes 37 and 39. The junction of the Patented June 3, 1969 parallel connected inductance coils 23 and 25 with the Hall semiconductor element 29 is coupled to the junction of the parallel connected silicon control rectifiers 31 and 33 with the primary winding of transformer through a series circuit that includes resistor 41, diode 43, diode and resistor 47. The junction of resistor 41 with diode 43 is connected to the control electrode or gate of silicon control rectifier 3'3 and the junction of resistor 47 with diode 45 is connected to the control electrode or gate of silicon control rectifier 31. The junction of the parallel connected inductance coils 23 and 25 with the Hall semiconductor element 29 is also coupled to the junction of the parallel connected silicon control rectifiers 31 and 33 with the primary winding of transformer 35 through the series connected diodes 49 and 51. The junction of diodes 49 and 51 is coupled to the junction of diodes 43 and 45 through resistor 53 and Zener diode 55. The variable arm of potentiometer 57 which is connected across the minor axis of the rectangular Hall semiconductor element 29 is coupled to ground through resistors 59 and 61. The junction of resistors .59 and 61 is connected to a first input circuit of DC. amplifier 63 and to the center tap of the secondary winding of transformer 35. The variable arm of potentiometer 65, the opposite ends of which are connected to the negative eight volt power supply line 67 and ground, is also coupled to ground through resistors 69 and 71. The junction of resistors 69 and 71 is connected to a second input circuit of DC. amplifier 63. As will be more apparent hereinafter, the parallel arrangement of resistors 73 and the series connected resistor 75 and condenser 77 across the input and output circuits of DC. amplifier 63 stablize and provide the proper transient response for the feedback loop of the amplifier. The out put circuit of DC. amplifier 63 is coupled to the base of transistor 79 through resistors 81 and 8 3. The junction of resistors 81 and 83 is coupled to ground through the anode cathode circuit of the silicon control rectifier 85 and also through the series connected resistor 87, Zener diode 89 and resistor 91. Condenser 93 is connected across resistor 91 as shown. The emitter-collector circuit of transistor 79 extends from the positive 15 volt supply line 95 through transistor 79, resistor 97 and the primary Winding of the satura'ble transformer 99 to ground. The secondary winding 101 of transformer 99 is connected in series with resistor 10:3 and condenser 105 across one end and the center tap of the secondary winding 107 of transformer 109. The primary winding of transformer 109 is connected across the input power conductors 3 and 5. Opposite ends of the secondary winding 107 of transformer 109 are coupled to one another by the series connected resistor 111 and condenser 113. The sinusoidal potential developed between the junction of resistor 111 and condenser 113 at point A and the junction of condenser 105 and the secondary winding of transformer 99 at point B is applied across the input of the full wave bridge circuit which includes diodes 115, 117, 119 and 121. The junction of diodes 119 and 121 is connected to the base of transistor 123 and the base of transistor 125. The supply voltage cricuit for transistors 123 and 125 includes the secondary winding 127 of transformer 109, diodes 129 and 13-1 and condenser 133. The emitter-collector circuit of transistor 123 extends from the junction of condenser 133 and diode 129 through resistors 135 and 137 and through the transistor to the junction of the center tap of secondary winding 127 of transformer 109 and condenser 133. The emitter-collector circuit of transistor 125 extends from the junction of condenser 133 and diode 131 through the transistor and through resistors 139 and 141 to the junction of the center tap of secondary winding 127 r of transformer 109 and condenser 133. The junction of diodes 115 and 121 is connected to one side of secondary 3 winding 127 of transformer 109 through resistor 143 and diode 145 and the junction of diodes 117 and 119 is connected to the other side of secondary winding 127 of transformer 109 through resistor 147 and diode 149. The junction of diodes 115 and 117 is connected to the center tap of secondary winding 127 of transformer 109.

Inasmuch as the details of the D.C. amplifier 63 per se form no part of the present invention, the same are not included herein for the sake of simplicity. For a full understading of the invention, it need only be understood that the amplifier 63 compares the D.C. output from the Hall unit with the D.C. voltage obtained from the brightness control potentiometer 65. Amplifier 63 provides a ditference output potential, which as will be more apparent hereinafter, is applied to the base of transistor 79.

In operation, when control switches 9 and 11 are closed, current from conductors 3 and energize power transformer 7 and current in its output circuit flows through the primary winding of transformer 21 as well as through the load 17. Current induced in the secondary winding of transformer 21, in turn, energizes the inductance coils 23 and 25 and develops the magnetic field for the Hall unit 27. Current through inductance coils 23 and 25 also flows through the semiconductor element 29 between one pair of opposite sides of the semiconductor and together with the magnetic field produced by inductance coils 23 and 25 develops an output potential across the other pair of opposite sides of the semiconductor. This output potential of the Hall unit 27 which is proportional to the square of the current through the primary and secondary circuits of transformer 21 is then fed into the D.C. amplifier '63 where it is compared with the preadjusted potential of the brightness control potentiometer 65. The

signal which is obtained at the output of the high gain amplifier 63 is proporional to the difference in the magnitude of the Hall unit potential and the potential of brightness contorl potentiometer 65. This difference signal is then amplified in transistor 79 and used to energize the primary winding of the saturable transformer 99. The transformer 99 provides, in effect, a variable saturable reactor in the R-C-L network of resistor 103, condenser 105 and inductor 101. This variable R-C-L network together with the RC network of resistor 111 and condenser 113 provides a signal across points A and B in the bridge circuit which varies in phase in excess of 200 with respect to the phase of the line voltage across the primary winding of transformer 109 as the saturation of the reactance of secondary winding 101 of transformer 99 is controlled. The parameters of the circuit are adjusted so that when a predetermined maximum amount of current flows through winding 101, the inductor is saturated and no phase shift is produced and when no current flows through winding 101, the signal across points A and B in the bridge circuit is 180 out of phase with the signal on input conductors 3 and 5. The sinusoidal output of the phase shift network is then rectified in the full wave bridge rectifier of diodes 115, 117, 119 and 121 and applied to the bases of transistors 123 and 125. Transistors 123 and 125 conduct during alternate half cycles of the input signal to the circuit and conrtol the gates of silicon control rectifiers 13 and 15. Thus, when the RMS current in the load circuit increases, the output potential of the Hall unit also increases. The output signal of D.C. amplifier 63 which increases corespondingly then increases the degree of D.C. saturation of winding 101 of transformer 99. This causes the signal which energizes the gates of silicon controlled rectifiers 13 and 15 to increase its lag of the line voltage and reduce the effective energization of the load circuit. An increase in current to the load is similarly effected in reverse when the RMS current to the load decreases.

The protection circuit, which comprises silicon controlled rectifiers 31 and 33, is provided to prevent damage to the Hall unit 27 from overloading. When the voltage developed across the Hall element exceeds a predetermined safe value, the gates of silicon conrtolled rectifiers 31 and 33 are triggered through diode 43 or diode 45 depending on the waveform polarity and the signal is shorted around Hall element 29. Diodes 4.3 and 45 direct the trigger voltage to the appropriate silicon controlled rectifier. Zener diode 55 and resistors 41, 47 and 53 determine the minimum voltage at which the silicon controlled rectitiers fire. Resistors 41 and 47 minimize the possibility of spurious triggering and also stabilize the operation of the silicon controlled rectifiers at high operating temperatures.

Shorting of the Hall element establishes under some conditions a runway load current condition. Transformer 35 and diodes 37 and 39 develop a voltage when either silicon control rectifier 31 or 33 is conducting which restores control.

The full range of control current is provided by transistor 79 when the D.C. amplifier output varies from 0 to approximately +3 volts. The Hall unit voltage input to the D.C. amplifier varies from 0 to approximately -0.15 volt, and the brightness control potentiometer input is approximately the same. The gain of the amplifier which is stabilized by resistor 73 is approximately 3300*. This excess gain causes the feedback loop to require correction through the main silicon control rectifiers 13 and 15 until the Hall unit output balances the preset level of the brightness control voltage.

Resistor and capacitor 77 provide the proper transient response to the feedback loop. Settlingtime of the system is approximately 0.1 second.

When the load is removed from the regulator, the voltage across the load quickly drops to zero. When the brightness control potentiometer is set for any current other than zero and the load circuit is open, no current flows in the Hall circuit. As a result of the system imbalance, the D.C. amplifier output is driven toward +12 volts. When this voltage exceeds 5.6 volts, the Zener diode 89 breaks down, and the gate of the silicon control rectitier is energized. When silicon control rectifier 85 then conducts, transistor 79 is cut off, the main silicon control rectifiers 13 and 15 stop conducting and the voltage to the load drops to zero.

What is claimed is:

1. Circuitry for maintaining a constant current from an input circuit to an output circuit, said circuitry comprising:

(a) a pair of silicon control rectifiers connected in inverse parallel relationship in the input circuit;

(b) means coupled to the output circuit for providing a potential which is proportional to the square of the current through the output circuit;

(c) a source of electrical energy;

(d) means coupled to the electrical energy source and to the means for providing the potential proportional to the square of the output circuit current for providing a potential proportional to the difference therebetween;

(e) a phase shifting network including a transformer having a primary winding that is energized by the input circuit and a secondary winding that energizes a series resistance-capacitance circuit connected across opposite extremities of the secondary winding and a series resistance-saturable reactor-capacitance circuit connected between the center tap and one of the extremities of the secondary winding;

(f) means responsive to the magnitude of the ditference potential for controlling the degree of saturation of the saturable reactor;

(g) and means coupling the output of the phase shift network to the gates of the silicon controlled rectifiers.

2. The circuitry substantially as described in claim 1 wherein the means coupled to the output circuit for providing a potential proportional to the square of the output circuit current is a Hall effect multiplier.

.5 6 3. The circuitry substantially as described in claim 2 3,176,215 3/1965 Kusko 323-24 and further including an overload protection circuit for 3,247,451 4/1966 Hauck. the Hall effect multiplier. 3,331,015 7/ 1967 Johnston.

4. The circuitry substantially as described in claim 3 3,348,129 10/1967 Schonholzer. and further including means for cutting off the silicon 5 control rectifiers when the load in the output circuit is JOHN Primary Examinerremoved. L

References Cited A. D. PE LINEN, Asszs an Examiner.

UNITED STATES PATENTS US. Cl. X.R. 3,132,287 5/1964 Yarbrough 323--24X 10 307--278; 31733; 323-24, 38, 94 

